Method for controlling a hybrid vehicle driveline

ABSTRACT

A method is provided to control a hybrid powertrain, comprising a combustion engine; a gearbox with input and output shafts, which combustion engine is connected to the input shaft; a first planetary gear connected to the input shaft; a second planetary gear connected to the first planetary gear; first and second electrical machines respectfully connected to the first and second planetary gears; first gear pair connected with the first planetary gear and output shaft; and second gear pair connected with the second planetary gear and output shaft. The method comprises: a) engaging gears in the first and second gear pairs; and b) connecting two rotatable components in the second planetary gear with a second coupling device.

CROSS-REFERENCE TO RELATED REFRENCE(S)

This application is a national stage application (filed under 35 §U.S.C.371) of PCT/SE15/050303, filed Mar. 17, 2015 of the same title, which,in turn claims priority to Swedish Application No. 1450322-1, filed Mar.20, 2014 of the same title; the contents of each of which are herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a method, vehicle and computer programproduct to control a hybrid powertrain.

BACKGROUND OF THE INVENTION

Hybrid vehicles may be driven by a primary engine, which may be acombustion engine, and a secondary engine, which may be an electricalmachine. The electrical machine is equipped with at least one energystorage device, such as an electro-chemical energy storage device, forstorage of electric power and control equipment to control the flow ofelectric power between the energy storage device and the electricalmachine. The electrical machine may thus alternately operate as a motorand as a generator, depending on the vehicle's operating mode. When thevehicle is braked, the electrical machine generates electric power,which is stored in the energy storage device. This is usually referredto as regenerative braking, which entails that the vehicle isdecelerated with the help of the electrical machine and the combustionengine. The stored electric power is used later for operation of thevehicle.

A gearbox in a hybrid vehicle may comprise a planetary gear. Theplanetary gearbox usually comprises three components, which arerotatably arranged in relation to each other, namely a sun wheel, aplanetary wheel carrier and an internal ring gear. With knowledge aboutthe number of cogs in the sun wheel and the internal ring gear, themutual speeds of the three components may be determined duringoperation. One of the components of the planetary gear may be connectedwith an output shaft in a combustion engine. This component of theplanetary gear thus rotates with a rotational speed corresponding to therotational speed of the output shaft in the combustion engine. A secondcomponent in the planetary gear may be connected with an input shaft toa transmission device. This component of the planetary gear thus rotateswith the same rotational speed as the input shaft to the transmissiondevice. A third component in the planetary gear is used to achievehybrid operation, connected with a rotor in an electrical machine. Thiscomponent in the planetary gear thus rotates with the same rotationalspeed as the rotor of the electrical machine, if they are directlyconnected with each other. Alternatively, the electrical machine may beconnected with the third component of the planetary gear via atransmission that has a gearing. In this case, the electrical machineand the third component in the planetary gear may rotate with differentrotational speeds. The engine speed and/or the torque of the electricalmachine may be controlled steplessly. During operating times when theinput shaft to the transmission device must be provided with a desiredrotational speed and/or torque, a control device having knowledge aboutthe engine speed of the combustion engine calculates the rotationalspeed with which the third component must be operated, in order for theinput shaft to the gearbox to obtain the desired rotational speed. Acontrol device activates the electrical machine, so that it provides thethird component with the calculated engine speed and thus the inputshaft to the transmission device with the desired rotational speed.

Depending on the design of the transmission device connected to theplanetary gear, a torque interruption between the gear steps may beavoided. Often, however, separate and complex devices are required inthe transmission device, in order to eliminate or reduce the torqueinterruption, so that a perception of stepless gear shifts is obtained.

By connecting the combustion engine's output shaft, the electricalmachine's rotor and the transmission device's input shaft with aplanetary gear, the conventional clutch mechanism may be avoided. Atacceleration of the vehicle, an increased torque must be delivered fromthe combustion engine and the electrical machine to the transmissiondevice, and further to the vehicle's driving wheels. Since both thecombustion engine and the electrical machine are connected with theplanetary gear, the largest possible torque delivered by the combustionengine and the electrical machine will be limited by one of these driveunits, namely the unit whose maximum torque is lower than the seconddrive unit's maximum torque, having regard to the gearing ratio betweenthem. In case the electrical machine's highest torque is lower than thecombustion engine's highest torque, having regard to the gearing betweenthem, the electrical machine will not be able to generate a sufficientlylarge reaction torque to the planetary gear, entailing that thecombustion engine may not transfer its highest torque to thetransmission device and further to the vehicle's driving wheels. Thus,the highest torque that may be transferred to the transmission device islimited by the electrical machine's strength. This is also apparent fromthe so-called planet equation.

Using a conventional clutch, which disconnects the gearbox's input shaftfrom the combustion engine during shifting processes in the gearbox,entails disadvantages, such as heating of the clutch's discs, resultingin wear of the clutch discs and an increased fuel consumption. Aconventional clutch mechanism is also relatively heavy and costly. Italso occupies a relatively large space in the vehicle.

In a vehicle, the space available for the drive arrangement is oftenlimited. If the drive arrangement comprises several components, such asa combustion engine, an electrical machine, a gearbox and a planetarygear, the construction must be compact. If there are additionalcomponents, such as a regenerative braking device, the requirements thatthe component parts must have a compact construction are even morestringent. At the same time, the component parts in the drivearrangement must be designed with dimensions that are able to absorb therequired forces and torque.

For some types of vehicles, especially heavy goods vehicles and buses, alarge number of gear steps is required. Thus, the number of componentparts in the gearbox increases, which must also be dimensioned to beable to absorb large forces and torque arising in such heavy goodsvehicles. This results in an increase of the size and weight of thegearbox.

There are also requirements for high reliability and high dependabilityof the components comprised in the drive device. In case the gearboxcomprises multi-plate clutches, a wear arises, which impacts thereliability and life of the gearbox.

At regenerative braking, kinetic energy is converted into electricpower, which is stored in an energy storage device, such asaccumulators. One factor impacting on the life of the energy storagedevice is the number of cycles in which the energy storage deviceprovides and extracts power to and from the electric machines. The morecycles, the shorter the life of the energy storage device.

Under some operating conditions, it is desirable to shut off thecombustion engine, with the objective of saving fuel and to avoidcooling down of the combustion engine's exhaust treatment system. Thevehicle is then driven by the electrical machine. When a torqueinjection is required in the hybrid powertrain, or when the energystorage device must be charged, the combustion engine must be startedquickly and efficiently.

In gearboxes with a large number of gear steps it is desirable, undersome operating conditions, to be able to achieve a desired gear withoutpassing all the gear steps in the gearbox and without any torqueinterruption in the powertrain.

The document EP-B1-1126987 shows a gearbox with double planetary gears.Each sun wheel of the planetary gear is connected to an electricalmachine, and the internal wheels of the planetary gears are connectedwith each other. The planetary wheel carrier in each planetary gear isconnected to a number of gear pairs, so that an infinite number of gearsteps is obtained. Another document, EP-B1-1280677, also shows how theplanetary gears may be bridged with a gear step arranged on thecombustion engine's output shaft.

The document US-A1-20050227803 shows a vehicle transmission with twoelectrical machines, connected to the respective sun wheels in twoplanetary gears. The planetary gears have a common planetary wheelcarrier, which is connected to the transmission's input shaft.

The document WO2008/046185-A1 shows a hybrid transmission with twoplanetary gears, wherein one electrical machine is connected to one ofthe planetary gears and a double clutch interacts with the secondplanetary gear. Both planetary gears also interact with each other via acogwheel transmission.

SUMMARY OF THE INVENTION

Despite prior art solutions in the field, there is a need to furtherdevelop a method to control a hybrid powertrain, in order to achieve thedesired gear with a small number of gear steps and without any torqueinterruption.

The objective of the invention is to provide a novel and advantageousmethod to reach the desired gear with a small number of gear steps,without any torque interruption in a hybrid powertrain.

Another objective of the invention is to provide a novel andadvantageous computer program to control a hybrid powertrain.

The method provides an efficient and reliable method to control a hybridpowertrain, comprising a combustion engine; a gearbox with an inputshaft and an output shaft, which combustion engine is connected to theinput shaft; a first planetary gear, which is connected to the inputshaft; a second planetary gear, connected to the first planetary gear; afirst electrical machine, connected to the first planetary gear; asecond electrical machine, connected to the second planetary gear; atleast one gear pair connected with the first planetary gear and theoutput shaft; and at least one gear pair connected with the secondplanetary gear and the output shaft. The method comprises the steps:engaging gears, corresponding to the at least one gear pair connectedwith the first planetary gear in the gearbox, and the gear pairconnected with the second planetary gear and the output shaft, andconnecting a second sun wheel, arranged in the second planetary gear,and a second planetary wheel carrier with each other, with the use of asecond coupling device. A coupling mechanism, arranged between the firstplanetary gear and the output shaft, is locked by way of controlling thecombustion engine in such a way that a synchronous engine speed isachieved between the first planetary gear and the output shaft; thefirst electrical machine is activated, so that the first electricalmachine generates a propulsion torque on the output shaft via thecoupling mechanism;

the at least one gear pair, which is connected with the second planetarygear and the output shaft, is disconnected from the countershaft whichgear pair was connected in the previous step, by controlling the secondelectrical machine and the combustion engine, connected with the firstplanetary gear, in such a way that a substantially zero torque state isachieved between the at least one gear pair, which is connected on thecountershaft and which is connected with the second planetary gear andthe output shaft, and the countershaft;

the at least one gear pair, which is connected with the second planetarygear and the output shaft which gear pair was not connected in theprevious step, is connected to the countershaft by way of controllingthe combustion engine, in such a way that a synchronous rotational speedis achieved between the at least one gear pair, which is connected withthe second planetary gear and the output shaft which gear pair was notpreviously connected, and the countershaft; and the second electricalmachine and the combustion engine, connected with the first planetarygear, is controlled to generate a propulsion torque on the output shaft.

According to one embodiment of the invention, at least one gear pair,which is joined with the countershaft and the output shaft is connected,so that the countershaft is connected with the output shaft.

According to an additional embodiment of the invention, the at least onegear pair connected with a countershaft and the output shaft comprises afifth and a sixth cogwheel in engagement with each other, which fifthcogwheel is arranged so that it may be connected with and disconnectedfrom the countershaft with the use of a fifth coupling element, whereatthe fifth cogwheel is connected with the countershaft.

According to an additional embodiment of the invention, the combustionengine is controlled in such a way that a synchronous rotational speedis achieved between the second sun wheel and the second planetary wheelcarrier, following which the second coupling device is shifted, andlocks the second sun wheel and the second planetary wheel carrier witheach other.

According to an additional embodiment of the invention, the at least onegear pair connected with the first planetary gear and the output shaftcomprises a first pinion gear and a first cogwheel, engaged with eachother, which first pinion gear is fixedly arranged with the firstplanetary gear, and which first cogwheel is arranged so that it may beconnected with and disconnected from a countershaft; and a third piniongear and a third cogwheel engaged with each other, which third piniongear is fixedly arranged with the first planetary gear, and which thirdcogwheel is arranged so that it may be connected with and disconnectedfrom the countershaft, whereat the first or the third cogwheel isconnected with the countershaft.

According to an additional embodiment of the invention the at least onegear pair connected with the second planetary gear and the output shaftcomprises a second pinion gear and also comprises a second cogwheelengaged with each other, which second pinion gear is fixedly arrangedwith the second planetary gear, and which second cogwheel is arranged sothat it may be connected with and disconnected from a countershaft; anda fourth pinion gear and a fourth cogwheel engaged with each other,which fourth pinion gear is fixedly arranged with the second planetarygear and which fourth cogwheel is arranged so that it may be connectedwith and disconnected from the countershaft, whereat the second or thefourth cogwheel is connected to the countershaft.

The electrical machines, which are connected to the planetary gears, maygenerate power and/or supply torque depending on the desired operatingmode. The electrical machines may also, at certain operating times,supply each other with power.

By connecting a first planetary wheel carrier in the first planetarygear, connected with a second sun wheel in the second planetary gear, afirst sun wheel in the first planetary gear, connected with the firstmain shaft, and a second planetary wheel carrier in the second planetarygear connected with the second main shaft, a transmission that shiftsgears without torque interruption may be obtained.

Suitably, a first planetary wheel carrier in the first planetary gear isdirectly connected with the combustion engine via the input shaft.Alternatively, the first planetary wheel carrier is connected with thecombustion engine via a coupling device. The second planetary wheelcarrier in the second planetary gear is suitably directly connected withthe second main shaft, and therefore with the transmission device. Thus,the hybrid powertrain may transfer a large torque in all operatingmodes, without being dependent on electric power from an energy storagedevice.

According to one embodiment, the first main shaft is connected with asun wheel, arranged in the first planetary gear. Alternatively, thefirst main shaft is connected with an internal ring gear arranged in thefirst planetary gear.

According to one embodiment, the second planetary gear is connected tothe first planetary gear by way of connecting the first planetary wheelcarrier with a second sun wheel, arranged in the second planetary gear.Alternatively, both the planetary gears are connected to each other byway of the first planetary wheel carrier being connected with a secondinternal ring gear, arranged in the second planetary gear.

The gearbox may preferably be equipped with a number of gear pairs,comprising cogwheels that may be mechanically locked with and releasedfrom a countershaft. Thus, a number of fixed gear steps is obtained,which may be shifted without torque interruption. The cogwheels that maybe locked on the countershaft also result in a compact construction withhigh reliability and high dependability. Alternatively, pinion gears inthe gear pairs may be arranged to be lockable and disconnectable on thefirst and/or second main shaft.

With the gearbox according to the invention conventional slip clutchesbetween the combustion engine and the gearbox may be avoided.

A locking mechanism is arranged to fixedly connect the combustionengine's output shaft with the gearbox housing. Thus, the firstplanetary wheel carrier will also be locked to the gearbox housing. Bylocking the combustion engine's output shaft with the locking mechanismand the first planetary wheel carrier with the gearbox's housing, thegearbox, and thus the vehicle, becomes adapted for electric operation bythe electrical machines. The electrical machines thus emit a torque tothe output shaft of the gearbox.

A first and second coupling device is arranged between the planetarywheel carrier and the sun wheel of the respective planetary gears. Thetask of the coupling devices is to lock the respective planetary wheelcarriers with the sun wheel. When the planetary wheel carrier and thesun wheel are connected with each other, the power from the combustionengine will pass through the planetary wheel carrier, the couplingdevice, the sun wheel and further along to the gearbox, which entailsthat the planetary wheels do not absorb any torque. This entails thatthe dimension of the planetary wheels may be adapted only to theelectrical machine's torque instead of the combustion engine's torque,which in turn means the planetary wheels may be designed with smallerdimensions. Thus, a drive arrangement according to the invention isobtained, which has a compact construction, a low weight and a lowmanufacturing cost.

The coupling devices and the locking mechanisms preferably comprise anannular sleeve, which is shifted axially between a connected and adisconnected state. The sleeve encloses, substantially concentrically,the gearbox's rotating components and is moved between the connected anddisconnected state with a power element. Thus, a compact construction isobtained, with a low weight and a low manufacturing cost.

In order to connect, with the first and the second coupling device,respectively, the sun wheel and the planetary wheel carrier of therespective planetary gear, the combustion engine and/or the firstelectrical machine and/or the second electrical machine is controlled insuch a way that a synchronous rotational speed is achieved between thesun wheel and the planetary wheel carrier. When a synchronous rotationalspeed has been achieved, the coupling device is shifted, so that the sunwheel and the planetary wheel carrier become mechanically connected witheach other.

In order to disconnect the respective planetary gear's planetary wheelcarrier and sun wheel from each other, the first and/or secondelectrical machine is controlled, so that torque balance is achieved inthe planetary gear. When torque balance has been achieved, the couplingdevice is shifted, so that the sun wheel and the planetary wheel carrierare no longer mechanically connected with to each other.

Torque balance relates to a state where a torque acts on an internalring gear arranged in the planetary gear, representing the product ofthe torque acting on the planetary wheel carrier of the planetary gearand the gear ratio of the planetary gear, while simultaneously a torqueacts on the planetary gear's sun wheel, representing the product of thetorque acting on the planetary wheel carrier and (1—the planetary gear'sgear ratio). In the event two of the planetary gear's component parts,i.e. the sun wheel, the internal ring gear or planetary wheel carriers,are connected with a coupling device, this coupling device does nottransfer any torque between the planetary gear's parts when torquebalance prevails. Accordingly, the coupling device may easily be shiftedand the planetary gear's component parts be disconnected.

BRIEF DESCRIPTION OF THE DRAWINGS

Below is a description, as an example, of preferred embodiments of theinvention with reference to the enclosed drawings, on which:

FIG. 1 schematically shows a vehicle in a side view with a combustionengine and a hybrid powertrain comprising a gearbox, which is controlledaccording to the present invention,

FIG. 2 shows a schematic side view of a hybrid powertrain with agearbox, which is controlled according to the present invention,

FIG. 3 shows a simplified schematic view of the hybrid powertrain inFIG. 2, and

FIG. 4 shows a flow chart of the method to control a gearbox accordingto the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a schematic side view of a vehicle 1, comprising a gearbox2 and a combustion engine 4, which are comprised in a hybrid powertrain3. The combustion engine 4 is connected to the gearbox 2, and thegearbox 2 is further connected to the driving wheels 6 of the vehicle 1via a propeller shaft 9. The driving wheels 6 are equipped with brakedevices 7 to brake the vehicle 1.

FIG. 2 shows a schematic side view of a hybrid powertrain 3 with agearbox 2, comprising an input shaft 8, a first and a second planetarygear 10 and 12, respectively, a first and a second electrical machine 14and 16, respectively, a countershaft 18 and an output shaft 20. Thehybrid powertrain comprises a combustion engine 4, connected to thegearbox 2. The combustion engine 4 is connected with the gearbox 2 viathe input shaft 8 of the gearbox. The combustion engine has an outputshaft 97. The output shaft 97 of the combustion engine 4 is connected tothe input shaft of the gearbox 2. The first planetary gear 10 has afirst internal ring gear 22, to which a first rotor 24 in the firstelectrical machine 14 is connected. The first planetary gear 10 also hasa first sun wheel 26 and a first planetary wheel carrier 50. The firstplanetary wheel carrier 50 is connected with the combustion engine 4 viathe input shaft 8 of the gearbox. The second planetary gear 12 has asecond internal ring gear 28, to which a second rotor 30 of the secondelectrical machine 16 is connected. The second planetary gear 12 has asecond sun wheel 32 and a second planetary wheel carrier 51. The firstand the second sun wheels 26 and 32, respectively, are coaxiallyarranged, which, according to the embodiment displayed, entails that afirst main shaft 34 arranged on the first sun wheel 26 extends inside asecond main shaft 36, which is equipped with a central boring 38,arranged on the second planetary wheel carrier 51. It is also possibleto arrange the first and second sun wheels 26 and 32, respectively, andalso the first main shaft 34 and the second main shaft 36, in parallelwith and next to each other. In this case, the countershaft 18 issuitably arranged between the first main shaft 34 and the second mainshaft 36, and the torque may be extracted directly from the countershaft18. The countershaft 18 thus constitutes, in this case, the output shaft20.

The combustion engine 4 is connected with the first planetary wheelcarrier 50, and the first planetary wheel carrier 50 is connected withthe second sun wheel 32.

The first electrical machine 14 is equipped with a first stator 40,which is connected to the vehicle 1, via a gear housing 42 surroundingthe gearbox 2. The second electrical machine 16 is equipped with asecond stator 44, which is connected to the vehicle 1, via a gearhousing 42 surrounding the gearbox 2. The first and the secondelectrical machine 16 are connected to an energy storage device 46, suchas a battery, which, depending on the vehicle's 1 operating mode,operates the electrical machines 14 and 16, respectively. At otheroperating modes, the electrical machines 14 and 16, respectively, maywork as generators, wherein power is supplied to the energy storagedevice 46. An electronic control device 48 is connected to the energystorage device 46 and controls the supply of power to the electricalmachines 14 and 16, respectively. Preferably the energy storage device46 is connected to the electrical machines 14 and 16, respectively, viaa switch 49, which is connected to the control device 48. In someoperating modes, the electrical machines 14 and 16, respectively, mayalso operate each other. Electric power is then led from one of theelectrical machines 14, 16 to the second electrical machine 14, 16 viathe switch 49, connected to the electrical machines 14, 16. Thus, it ispossible to achieve a power balance between the electrical machines 14,16. Another computer 53 may also be connected to the control device 48and the gearbox 2.

The first planetary gear 10 is equipped with a first planetary wheelcarrier 50, on which a first set of planetary wheels 52 is mounted. Thesecond planetary gear 12 is equipped with a second planetary wheelcarrier 51, on which a second set of planetary wheels 54 is mounted. Thefirst set of planetary wheels 52 interacts with the first internal ringgear 22 and the first sun wheel 26. The second set of planetary wheels54 interacts with the second internal ring gear 28 and the second sunwheel 32. The input shaft 8 of the gearbox 2 is connected with the firstplanetary wheel carrier 50.

A first coupling device 56 is arranged between the first sun wheel 26and the first planetary wheel carrier 50. By arranging the firstcoupling device 56 in such a way that the first sun wheel 26 and thefirst planetary wheel carrier 50 are connected with each other, and maytherefore not rotate in relation to each other, the first planetarywheel carrier 50 and the first sun wheel 26 will rotate with equalrotational speeds.

A second coupling device 58 is arranged between the second sun wheel 32and the second planetary wheel carrier 51. By arranging the secondcoupling device 58 in such a way that the second sun wheel 32 and thesecond planetary wheel carrier 51 are connected with each other, and maytherefore not rotate in relation to each other, the second planetarywheel carrier 51 and the first sun wheel 32 will rotate with equalrotational speeds.

Preferably, the first and second coupling devices 56, 58 comprise afirst and a second splines-equipped coupling sleeve 55 and 57,respectively, which is axially shiftable on a splines-equipped sectionon the first and second, respectively, planetary wheel carrier 50 and51, and on a splines-equipped section on the respective sun wheels 26and 32. By shifting the respective coupling sleeve 55, 57 so that thesplines-equipped sections are connected via the respective couplingsleeves 55, 57, the first planetary wheel carrier 50 and the first sunwheel 26, as well as the second planetary wheel carrier 51 and thesecond sun wheel 32, respectively, become mutually interlocked with eachother and may not rotate in relation to each other.

The first and second coupling device 56, 58 according to the embodimentdisplayed in FIG. 2 are arranged between the first sun wheel 26 and thefirst planetary wheel carrier 50, and between the second sun wheel 28and the second planetary wheel carrier 51, respectively. However, it ispossible to arrange an additional or alternative coupling device (notdisplayed) between the first internal ring gear 22 and the firstplanetary wheel carrier 50, and also to arrange an additional oralternative coupling device (not displayed) between the second internalring gear 28 and the second planetary wheel carrier 51.

The first planetary wheel carrier 50 of the first planetary gear 10 inthis embodiment is fixedly connected with the second sun wheel 32 of thesecond planetary gear 12. Alternatively, the first planetary wheelcarrier 50 is fixedly connected with the second internal ring gear 28 ofthe second planetary gear 12.

A transmission device 19, which comprises a first gear pair 60, arrangedbetween the first planetary gear 10 and the output shaft 20 is connectedto the first and the second main shaft 34, 36. The first gear pair 60comprises a first pinion gear 62 and a first cogwheel 64, which are inengagement with each other. A second gear pair 66 is arranged betweenthe second planetary gear 12 and the output shaft 20. The second gearpair 66 comprises a second pinion gear 68 and a second cogwheel 70,which are in engagement with each other. A third gear pair 72 isarranged between the first planetary gear 10 and the output shaft 20.The third gear pair 72 comprises a third pinion gear 74 and a thirdcogwheel 76, which are in engagement with each other. A fourth gear pair78 is arranged between the second planetary gear 12 and the output shaft20. The fourth gear pair 78 comprises a fourth pinion gear 80 and afourth cogwheel 82, which are in engagement with each other.

On the first main shaft 34, the first and the third pinion gears 62 and74, respectively, are arranged. The first and the third pinion gears 62and 74, respectively, are fixedly connected with the first main shaft34, so that they may not rotate in relation to the first main shaft 34.On the second main shaft 36, the second and the fourth pinion gears 68and 80, respectively, are arranged. The second and the fourth piniongears 68 and 80, respectively, are fixedly connected with the secondmain shaft 36, so that they may not rotate in relation to the secondmain shaft 36.

The countershaft 18 extends substantially in parallel with the first andthe second main shaft 34 and 36, respectively. On the countershaft 18,the first, second, third and fourth cogwheels 64, 70, 76 and 82,respectively, are mounted. The first pinion gear 62 engages with thefirst cogwheel 64, the second pinion gear 68 engages with the secondcogwheel 70, the third pinion gear 74 engages with the third cogwheel 76and the fourth pinion gear 80 engages with the fourth cogwheel 82.

The first, second, third and fourth cogwheels 64, 70, 76 and 82,respectively, may be individually locked with and released from thecountershaft 18 with the assistance of the first, second, third andfourth coupling elements 84, 86, 88 and 90, respectively. The couplingelements 84, 86, 88 and 90, respectively, preferably consist ofsplines-equipped sections on the cogwheels 64, 70, 76 and 82,respectively, and on the countershaft 18, which interact with fifth andsixth coupling sleeves 83, 85 which engage mechanically with thesplines-equipped sections of the respective first to fourth cogwheel 64,70, 76 and 82 and of the countershaft 18. The first and third couplingelements 84, 88 are preferably equipped with a common coupling sleeve83, and the second and fourth coupling elements 86, 90 are preferablyequipped with a common coupling sleeve 85. In the released state, arelative rotation may occur between the cogwheels 64, 70, 76 and 82 andof the countershaft 18. The coupling elements 84, 86, 88 and 90,respectively, may also consist of friction clutches. On the countershaft18 a fifth cogwheel 92 is also arranged, which engages with a sixthcogwheel 94, which is arranged on the output shaft 20 of the gearbox 2.

The countershaft 18 is arranged between the respective first and secondplanetary gears 10, 12 and the output shaft 20, so that the countershaft18 is connected with the output shaft 20 via a fifth gear pair 21, whichcomprises the fifth and the sixth cogwheel 92, 94. The fifth cogwheel 92is arranged so it may be connected with and disconnected from thecountershaft 18 with a fifth coupling element 93.

By disconnecting the fifth cogwheel 92, which is arranged to bedisconnectable from the countershaft 18, it is possible to transfertorque from the second planetary gear 12 to the countershaft 18 via, forexample, the second gear pair 66, and to further transfer torque fromthe countershaft 18 to the output shaft 20 via, for example, the firstgear pair 60. Thus, a number of gear steps is obtained, wherein torquefrom one of the planetary gears 10, 12 may be transferred to thecountershaft 18, and further along from the countershaft 18 to the mainshaft 34, 36 connected with the second planetary gear 10, 12, finally totransfer torque to the output shaft 20 of the gearbox 2. This presumes,however, that a coupling mechanism 96 arranged between the first mainshaft 34 and the output shaft 20 is connected, which is described inmore detail below.

The fifth cogwheel 92 may be locked to and released from thecountershaft 18 with the assistance of a fifth coupling element 93. Thecoupling element 93 preferably consists of splines-equipped sectionsadapted on the fifth cogwheel 92 and the countershaft 18, which sectionsinteract with a ninth coupling sleeve 87, which engages mechanicallywith the splines-equipped sections of the fifth cogwheel 92 and thecountershaft 18. In the released state, a relative rotation may occurbetween the fifth cogwheel 92 and the countershaft 18. The fifthcoupling element 93 may also consist of friction clutches.

Torque transfer from the input shaft 8 of the gearbox 2 to the outputshaft 20 of the gearbox 2 may occur via the first or the secondplanetary gear 10 and 12, respectively, and the countershaft 18. Thetorque transfer may also occur directly via the first planetary gear 10,whose first sun wheel 26 is connected, via the first main shaft 34, tothe output shaft 20 of the gearbox 2 via a coupling mechanism 96. Thecoupling mechanism 96 preferably comprises a splines-equipped seventhcoupling sleeve 100, which is axially shiftable on the first main shaft34 and on the splines-equipped sections of the output shaft 20. Byshifting the seventh coupling sleeve 100, so that the splines-equippedsections are connected via the seventh coupling sleeve 100, the firstmain shaft 34 becomes locked with the output shaft 20, which, whenrotating, will therefore have the same rotational speed. Bydisconnecting the fifth cogwheel 92 of the fifth gear pair 21 from thecountershaft 18, torque from the second planetary gear 12 may betransferred to the countershaft 18, and further along from thecountershaft 18 to the first main shaft 34, connected with the firstplanetary gear 10, in order finally to transfer torque via the couplingmechanism 96 to the output shaft 20 of the gearbox 2.

In some operating modes the gearbox 2 may operate so that one of the sunwheels 26 and 32, respectively, are locked with the first and the secondplanetary wheel carrier 50 and 51, respectively, with the help of thefirst and the second coupling device 56 and 58, respectively. The firstand the second main shaft 34 and 36, respectively, then obtain the samerotational speed as the input shaft 8 of the gearbox 2, depending onwhich sun wheel 26 and 32, respectively, is locked with the respectiveplanetary wheel carriers 50 and 51. One or both of the electricalmachines 14 and 16, respectively, may operate as a generator to generateelectric power to the energy storage device 46. Alternatively, theelectrical machine 14 and 16, respectively, may provide a torqueinjection, in order to thus increase the torque in the output shaft 20.At some operating times, the electrical machines 14 and 16,respectively, will supply each other with electric power, independentlyof the energy storage device 46.

It is also possible that both the first and the second electricalmachine 14 and 16, respectively, generate power to the energy storagedevice 46. At engine braking the driver releases the accelerator pedal(not displayed) of the vehicle 1. The output shaft 20 of the gearbox 2then operates one or both electrical machines 14 and 16, respectively,while the combustion engine 4 and the electrical machines 14 and 16,respectively, engine brake. The electrical machines 14 and 16,respectively, in this case generate electric power, which is stored inthe energy storage device 46 in the vehicle 1. This operating state isreferred to as regenerative braking. In order to facilitate morepowerful braking effect the output shaft 97 of the combustion engine's 4may be locked and thus be prevented from rotating. Thus, only one of orboth the electrical machines 14 and 16, respectively, will function asbrakes and 16 generate electric power, which is stored in the energystorage device 46. The locking of the output shaft 97 of the combustionengine 4 may also be carried out when the vehicle must accelerate byonly one or both the electrical machines 14 and 16, respectively. If thetorque of one or both of the respective electrical machines 14 and 16overcomes the torque off the combustion engine 4, and having regard tothe gearing between them, the combustion engine 4 will not be able toresist the large torque which the respective electrical machines 14 and16 generate, so that it becomes necessary to lock the output shaft 97 ofthe combustion engine's 4. The locking of the output shaft 97 of thecombustion engine 4 is preferably carried out with a locking device 102,which is arranged between the first planetary wheel carrier 50 and thegear hosing 42. By locking the first planetary wheel carrier 50 and thegear housing 42, the output shaft 97 of the combustion engine 4 willalso be locked, since the output shaft 97 of the combustion engines 4 isconnected with the first planetary wheel carrier 50 via the input shaft8 of the gearbox. The locking device 102 preferably comprises asplines-equipped eighth coupling sleeve 104, which is axially shiftableon a splines-equipped section of the first planetary wheel carrier 50,and on a splines-equipped section of the gear housing. By shifting theeight coupling sleeve 104 so that the splines-equipped sections areconnected via the coupling sleeve 104, the first planetary wheel carrier50, and therefore the output shaft 97 of the combustion engine 4 isprevented from rotating.

The control device 48 is connected to the electrical machines 14 and 16,respectively, to control the respective electrical machines 14 and 16,so that they, during certain operating times, use stored electric powerto supply driving power to the output shaft 20 of the gearbox 2, andduring other operating times use the kinetic energy of the output shaft20 of the gearbox 2 to extract and store electric power. The controldevice 48 thus detects the rotational speed and/or the torque of theoutput shaft 97 of the combustion engine 4 via sensors 98 arranged atthe electrical machines 14 and 16, respectively, and in the output shaft20 of the gearbox 2, in order thus to gather information and to controlthe electrical machines 14 and 16, respectively, to operate as electricmotors or generators. The control device 48 may be a computer withsoftware suitable for this purpose. The control device 48 also controlsthe flow of power between the energy storage device 46 and therespective stators 40 and 44 of the electrical machines 14 and 16,respectively. At times when the electrical machines 14 and 16,respectively, operate as engines, stored electric power is supplied fromthe energy storage device 46 to the respective stators 40 and 44. Attimes when the electrical machines 14 and 16 operate as generatorselectric power is supplied from the respective stators 40 and 44 to theenergy storage device 46. However, as stated above, the electricalmachines 14 and 16, respectively, may, during certain operating times,supply each other with electric power, independently of the energystorage device 46.

The first and the second coupling devices 56 and 58, respectively, thefirst, second, third, fourth and fifth coupling elements 84, 86, 88, 90and 93, respectively, the coupling mechanism 96 between the first mainshaft 34 and the output shaft 20, and the locking device 102 between thefirst planetary wheel carrier 50 and the gear housing 42, are connectedto the control device 48 via their respective coupling sleeves. Thesecomponents are preferably activated and deactivated by electric signalsfrom the control device 48. The coupling sleeves are preferably shiftedby non-displayed power elements, such as hydraulically or pneumaticallyoperated cylinders. It is also possible to shift the coupling sleeveswith electrically powered power elements.

The example embodiment in FIG. 2 shows four pinion gears 62, 68, 74 and80, respectively, and four cogwheels 64, 70, 76 and 82, respectively,and two respective planetary gears 10 and 12, with associated electricalmachines 14 and 16, respectively. However, it is possible to adapt thegearbox 2 with more or fewer pinion gears and cogwheels, and with moreplanetary gears with associated electrical machines.

FIG. 3 illustrates the hybrid powertrain 3 according to FIG. 2 in asimplified view, where some components have been excluded in theinterest of clarity. G1 in FIG. 3 consists of at least one gear pairconnected with the first main shaft 34 and therefore with the firstplanetary gear 10, and a gear pair G2 consists of at least one gear pairconnected with the second main shaft 36 and therefore with the secondplanetary gear 12. These gear pairs G1, G2 are also connected to theoutput shaft 20 via the countershaft 18. G1 and G2, respectively, mayconsist of one or several gear pairs. The gear pair G1, connected withthe first planetary gear 10, may for example consist of the first gearpair 60 and/or the third gear pair 72, as described in FIG. 2. The gearpair G2, connected with the second planetary gear 12, may for exampleconsist of the second gear pair 66 and/or the fourth gear pair 78, asdescribed in FIG. 2. Further, at least one gear pair G3, connected withthe output shaft 20 and the countershaft, 18 is displayed, which mayconsist of the fifth gear pair 21 described in FIG. 2. G3 may consist ofone or several gear pairs. Alternatively, torque may be extracteddirectly from the countershaft 18, which thus constitutes the outputshaft.

The at least one gear pair G1, 60, 72, connected with the firstplanetary gear 10 comprises at least one pinion gear 62, 74 and onecogwheel 64, 76 arranged in engagement with each other, which piniongear 62, 74 may be arranged in such a way that it may be connected withand disconnected from the main shaft 34, arranged with the firstplanetary gear 10. The at least one cogwheel 64, 76 may be arranged sothat it may be connected with and disconnected from the countershaft 18.

The at least one gear pair G2, 66, 78, connected with the secondplanetary gear 12, comprises at least one pinion gear 68, 80 and onecogwheel 70, 82 arranged in engagement with each other, which piniongear 68, 80 may be arranged in such a way that it may be connected withand disconnected from the second main shaft 36, arranged with the firstplanetary gear 12. The at least one cogwheel 70, 82 may be arranged sothat it may be connected with and disconnected from the countershaft 18.

As described, torque is extracted from the gearbox 2 from the outputshaft 20. It is also possible to extract torque directly from the firstor second main shaft 34, 36, or directly from the countershaft 18, whichin this case constitutes the output shaft 20. Torque may also beextracted in parallel from two or all of the three shafts 18, 34, 36simultaneously.

Below, an up-shift from a first to a seventh gear will be described,wherein the gearbox 2 is arranged in a vehicle 1 and the vehicle ispropelled by the combustion engine 4. The description of the up-shiftwill comprise components that are not displayed in the simplified FIG.3, but which are displayed in FIG. 2.

The input shaft 8 of the gearbox 2 is connected to the output shaft 97of the vehicle's 1 combustion engine 4. The output shaft 20 of thegearbox 2 is connected to a driving shaft 99 in the vehicle 1. At idlingof the combustion engine 4 and when the vehicle 1 is at a standstill,the input shaft 8 of the gearbox 2 rotates at the same time as theoutput shaft 20 of the gearbox 2 is at a standstill. The locking device102 is deactivated, so that the output shaft 97 of the combustion engine4 may rotate freely. Since the input shaft 8 of the gearbox 2 rotates,the first planetary wheel carrier 50 will also rotate, which entailsthat the first set of planetary wheels 52 will rotate. Since the firstplanetary wheel carrier 50 is connected to the second sun wheel 32, thesecond sun wheel 32, and thus also the second set of planetary wheels54, will rotate. By not supplying power to the first and the secondelectrical machines 14 and 16, respectively, the first and the secondinternal rings 22 and 28, respectively, which are connected with therespective first and second rotor 24 and 30 of the electrical machines14 and 16, respectively, will rotate freely, so that no torque isabsorbed by the respective internal rings 22 and 28. The first and thesecond coupling devices 56 and 58, respectively, are disconnected andthus not actuated. Thus, no torque will be transferred from thecombustion engine 4 to the sun wheel 26 of the first planetary gear 10or to the planetary wheel carrier 51 of the second planetary gear 12.The coupling mechanism 96 between the first main shaft 34 and the outputshaft 20 is disconnected, so that the first main shaft 34 and the outputshaft 20 may rotate freely in relation to each other. Since the firstplanetary gear's sun wheel 26, the planetary wheel carrier 51 of thesecond planetary gear 12 and the output shaft 20 of the gearbox 2 are,at this stage, at a standstill, the countershaft 18 is also at astandstill. In a first step the fourth cogwheel 82 and the thirdcogwheel 76 are connected with the countershaft 18 with the assistanceof the fourth and third coupling elements 90 and 88, respectively. Thefirst cogwheel 64 and the second cogwheel 70 are disconnected from thecountershaft 18. Thus, the first cogwheel 64 and the second cogwheel 70are allowed to rotate freely in relation to the countershaft 18. Thefifth cogwheel 92 of the fifth gear pair 21 is locked on thecountershaft 18 with the assistance of the fifth coupling element 93.

In order to start the rotation of the output shaft 20 of the gearbox 2,with the objective of driving the vehicle 1, the fourth pinion gear 80and the fourth cogwheel 82 on the countershaft 18 must be brought torotate. This is achieved by making the second planetary wheel carrier 51rotate. When the second planetary wheel carrier 51 rotates, the secondmain shaft 36 will also rotate and thus the fourth pinion gear 80, whichis arranged on the second main shaft 36, also rotates. The secondplanetary wheel carrier 51 is made to rotate by controlling the secondinternal ring gear 28 with the second electrical machine 16. Byactivating the second electrical machine 16 and controlling thecombustion engine 4 to a suitable engine speed, the vehicle 1 begins tomove as the second main shaft 36 begins to rotate. When the secondplanetary wheel carrier 51 and the second sun wheel 32 achieve the samerotational speed, the second sun wheel 32 is locked with the secondplanetary wheel carrier 51 with the assistance of the second couplingdevice 58. As mentioned above, the second coupling device 58 ispreferably adapted in such a way that the second sun wheel 32 and thesecond planetary wheel carrier 51 engage mechanically with each other.Alternatively, the second coupling device 58 may be adapted as a slipbrake or a multi-plate clutch which connects, in a smooth way, thesecond sun wheel 32 with the second planetary wheel carrier 51. When thesecond sun wheel 32 is connected with the second planetary wheel carrier51, the second planetary wheel carrier 51 will rotate with the samerotational speed as the output shaft 97 of the combustion engine 4.Thus, the torque generated by the combustion engine 4 is transferred tothe output shaft 20 of the gearbox 2 via the fourth pinion gear 80, thefourth cogwheel 82 on the countershaft 18, the fifth cogwheel 92 on thecountershaft 18, and the sixth cogwheel 94 on the output shaft 20 of thegearbox 2. The vehicle 1 will thus begin to move off and be propelled bya first gear.

When the countershaft 18 is made to rotate by the fourth cogwheel 82 onthe countershaft 18, the third cogwheel 76 on the countershaft 18 willalso rotate. Thus, the countershaft 18 operates the third cogwheel 76,which in turn operates the third pinion gear 74 on the first main shaft34. When the first main shaft 34 rotates, the first sun wheel 26 willalso rotate, and thus, depending on the rotational speed of the outputshaft 97 of the combustion engine 4 and thus the rotational speed of thefirst planetary wheel carrier 50, it will cause the first internal ringgear 22 and the first rotor 24 of the first electrical machine 14 torotate. It is thus possible to allow the first electrical machine 14 tooperate as a generator to supply power to the energy storage device 46,and/or to supply power to the second electrical machine 16. It is alsopossible for the second electrical machine 16 to be operated as agenerator. Alternatively, the first electrical machine 14 may emit atorque injection, by way of the control device 48 controlling the firstelectrical machine 14 to provide a driving torque.

In order to shift from a first gear to a second gear, the lockingbetween the second sun wheel 32 and the second planetary wheel carrier51 must cease, which is achieved by way of the first electrical machine14 and/or the second electrical machine 16 being controlled in such away that torque balance prevails in the second planetary gear 12.Subsequently, the second coupling device 58 is controlled, so that itdisconnects the second sun wheel 32 and the second planetary wheelcarrier 51 from each other. The second gear is connected, by way of thecontrol device 48 controlling the combustion engine 4, so that asynchronous rotational speed arises between the first planetary wheelcarrier 50 and the first sun wheel 26, in order to achieve a lockingbetween the first planetary wheel carrier 50 and the first sun wheel 26.This is achieved by way of controlling the first coupling device 56 insuch a way that the first planetary wheel carrier 50 and the first sunwheel 26 are mechanically connected with each other. Alternatively, thefirst coupling device 56 may be adapted as a slip brake or a multi-plateclutch which connects, in a smooth way, the first sun wheel 26 with thefirst planetary wheel carrier 50. By synchronizing the control of thesecond and first electrical machines 14 and 16, respectively, a soft anddisruption-free transition from a first to a second gear may be carriedout.

The first main shaft 34 now rotates, operated by the output shaft 97 ofthe combustion engine 4, and the first main shaft 34 now operates thethird pinion gear 74. The first planetary wheel carrier 50 thus operatesthe third pinion gear 74 via the first sun wheel 26 and the first mainshaft 34. Since the third cogwheel 76 is in engagement with the thirdpinion gear 74 and is connected with the countershaft 18, the thirdcogwheel 76 will operate the countershaft 18, which in turn operates thefifth cogwheel 92 on the countershaft 18. The fifth cogwheel 92 in turnoperates the output shaft 20 of the gearbox 2 via the sixth cogwheel 94,which is arranged on the output shaft 20 of the gearbox 2. The vehicle 1is now operated with a second gear.

When the countershaft 18 is made to rotate by the third cogwheel 76, thefourth cogwheel 82 will also rotate. Thus, the countershaft 18 operatesthe fourth cogwheel 82, which in turn operates the fourth pinion gear 80on the second main shaft 36. When the second main shaft 36 rotates, thesecond planetary wheel carrier 51 will also rotate, and thus, dependingon the rotational speed of the output shaft 97 of the combustion engine4, and thus the rotational speed in the first planetary wheel carrier50, it will cause the second internal ring gear 28 and the second rotor30 of the second electrical machine 16 to rotate. It is thus possible toallow the second electrical machine 16 to operate as a generator tosupply power to the energy storage device 46, and/or to supply power tothe first electrical machine 14. The second electrical machine 16 mayalso emit a torque injection, by way of the control device 48controlling the second electrical machine 16 to provide a propulsiontorque.

In order to shift from a second gear to a third gear, the fourthcogwheel 82 on the countershaft 18 must be disconnected from thecountershaft 18 with the fourth coupling element 90, so that the fourthcogwheel 82 may rotate freely in relation to the countershaft 18.Subsequently, the countershaft 18 is connected with the second cogwheel70 on the countershaft 18 via the second coupling element 86. In orderto achieve a connection of the countershaft 18 and the second cogwheel70 on the countershaft 18, preferably the second electrical machine 16is controlled in such a way that a synchronous rotational speed arisesbetween the countershaft 18 and the second cogwheel 70 on thecountershaft 18. A synchronous rotational speed may be achieved by wayof measuring the rotational speed in the second rotor 30 in the secondelectrical machine 16, and measuring the rotational speed in the outputshaft 20. Thus, the rotational speed in the second main shaft 36 and therotational speed in the countershaft 18 may be determined by way ofgiven gear ratios. The rotational speed of the respective shafts 18, 36is controlled, and when a synchronous rotational speed has arisenbetween the countershaft 18 and the second cogwheel 70, the countershaft18 and the second cogwheel 70 are connected with the assistance of thesecond coupling element 86.

In order to complete the shift from a second gear to a third gear, thelocking between the first sun wheel 26 and the first planetary wheelcarrier 50 must cease, which is achieved by way of the first and/or thesecond electrical machine 14, 16 being controlled in such a way thattorque balance prevails in the first planetary gear 10, following whichthe first coupling device 56 is controlled, so that it disconnects thefirst sun wheel 26 and the first planetary wheel carrier 50 from eachother. Subsequently, the combustion engine 4 is controlled in such a waythat a synchronous rotational speed arises between the second sun wheel32 and the second planetary wheel carrier 51, so that the secondcoupling device 58 may be engaged in order thus to connect the secondsun wheel 32 with the second planetary wheel carrier 51, via thecoupling sleeve 57. By synchronizing the control of the second and firstelectrical machines 14 and 16, respectively, a soft and disruption-freetransition from a second to a third gear may be carried out.

The third cogwheel 76 is disconnected by controlling the firstelectrical machine 14 in such a way that a substantially zero torquestate arises between the countershaft 18 and the third cogwheel 76. Whena substantially zero torque state arises, the third cogwheel 76 isdisconnected from the countershaft 18 by controlling the third couplingelement 88, so that it releases the third cogwheel 76 from thecountershaft 18. Subsequently, the first electrical machine 14 iscontrolled in such a way that a synchronous rotational speed arisesbetween the countershaft 18 and the first cogwheel 64. When asynchronous rotational speed arises, the first cogwheel 64 is connectedto the countershaft 18 by way of controlling the first coupling element84, so that it connects the first cogwheel 64 on the countershaft 18. Asynchronous rotational speed may be achieved, since the rotational speedof the first rotor 24 in the first electrical machine 14 is measured,and the rotational speed of the output shaft 20 is measured, followingwhich the rotational speeds of the shafts 18, 34 are controlled in sucha way that a synchronous rotational speed arises. Thus, the rotationalspeed of the first main shaft 34 and the rotational speed of thecountershaft 18 may be determined by way of given gear ratios.

The second main shaft 36 now rotates with the same rotational speed asthe output shaft 97 of the combustion engine 4, and the second mainshaft 36 now operates the second pinion gear 68 via the second mainshaft 36. Since the second cogwheel 70 is in engagement with the secondpinion gear 68 and is connected with the countershaft 18, the secondcogwheel 70 will operate the countershaft 18, which in turn operates thefifth cogwheel 92 on the countershaft 18. The fifth cogwheel 92 in turnoperates the output shaft 20 of the gearbox 2 via the sixth cogwheel 94,which is arranged on the output shaft 20 of the gearbox 2. The vehicle 1is now driven in a third gear.

When the countershaft 18 is made to rotate by the second cogwheel 70 onthe countershaft 18, the first cogwheel 64 on the countershaft 18 willalso rotate. Thus, the countershaft 18 operates the first cogwheel 64,which in turn operates the first pinion gear 62 on the first main shaft34. When the first main shaft 34 rotates, the first sun wheel 26 willalso rotate, and thus, depending on the rotational speed of the outputshaft 97 of the combustion engine 4 and thus the rotational speed of thefirst planetary wheel carrier 50, it will cause the first internal ringgear 22 and the first rotor 24 of the first electrical machine 14 torotate. It is thus possible to allow the first electrical machine 14operate as a generator to supply power to the energy storage device 46,and/or to supply power to the second electrical machine 16.Alternatively, the first electrical machine 14 may emit a torqueinjection, by way of the control device 48 controlling the firstelectrical machine 14 to provide a driving torque.

In order to complete the shift from the third to the fourth gear, thelocking between the second sun wheel 32 and the second planetary wheelcarrier 51 must cease, which is achieved by way of the first and/or thesecond electrical machine 14, 16 being controlled in such a way thattorque balance prevails in the second planetary gear 12, following whichthe second coupling device 58 is controlled in such a way that itdisconnects the second sun wheel 32 and the second planetary wheelcarrier 51 from each other. A fourth gear is subsequently connected byway of the control device 48 controlling the combustion engine 4, sothat a synchronous rotational speed arises between the first planetarywheel carrier 50 and the first sun wheel 26, to achieve a lockingbetween the first planetary wheel carrier 50 and the first sun wheel 26.This is achieved by way of controlling the first coupling device 56 insuch a way that the first planetary wheel carrier 50 and the first sunwheel 26 are mechanically connected with each other. By synchronizingthe control of the combustion engine 2 and the second and firstelectrical machine 14 and 16 a soft and disruption-free transition froma third to a fourth gear may be carried out.

The first main shaft 34 now rotates and is operated by the output shaft97 of the combustion engine 4 and the first main shaft 34 now operatesthe first pinion gear 62. The first planetary wheel carrier 50 thusoperates the first pinion gear 62 via the first sun wheel 26 and thefirst main shaft 34. Since the first cogwheel 64 is in engagement withthe first pinion gear 62 and is connected with the countershaft 18, thefirst cogwheel 64 will operate the countershaft 18, which in turnoperates the fifth cogwheel 92 on the countershaft 18. The fifthcogwheel 92 in turn operates the output shaft 20 of the gearbox 2 viathe sixth cogwheel 94, which is arranged on the output shaft 20 of thegearbox 2. The vehicle 1 is now driven in a fourth gear.

When the countershaft 18 is made to rotate by the first cogwheel 64, thesecond cogwheel 70 will also rotate. Thus, the countershaft 18 operatesthe second cogwheel 70, which in turn operates the second pinion gear 68on the second main shaft 36. When the second main shaft 36 rotates, thesecond planetary wheel carrier 51 will also rotate, and thus, dependingon the rotational speed of the output shaft 97 of the combustion engine4, and thus the rotational speed in the first planetary wheel carrier50, it will cause the second internal ring gear 28 and the second rotor30 of the second electrical machine 16 to rotate. It is thus possible toallow the second electrical machine 16 to operate as a generator tosupply power to the energy storage device 46, and/or to supply power tothe first electrical machine 14. The second electrical machine 16 mayalso emit a torque injection, by way of the control device 48controlling the second electrical machine 16 to provide a propulsiontorque.

In order to shift from a fourth gear to a fifth gear, the secondelectrical machine is activated to transfer the propulsion torque viathe second gear pair 66, following which the first cogwheel 64 isdisengaged from the countershaft 18, so that the fourth gear isdisconnected. This is achieved by way of controlling the combustionengine 4 and the first electrical machine 14, in such a way that thefirst cogwheel 64 is brought to a substantially zero torque state inrelation to the countershaft 18. When a substantially zero torque statehas arisen, the first coupling element 84 is disengaged, so that thefirst cogwheel 64 is disconnected from the countershaft 18.

Subsequently, torque balance is created in the first planetary gear 10,following which the first coupling device 56 is disconnected.Subsequently, the rotational speed of the first main shaft 34 issynchronized with the rotational speed of the output shaft 20, followingwhich the coupling mechanism 96 is controlled in such a way that itconnects the first main shaft 34 with the output shaft 20.

Subsequently, the combustion engine 4 and the first electrical machine14 are controlled in such a way that the propulsion torque occurs viathe first main shaft 34 and via the coupling mechanism 96, and furtheralong to the output shaft 20. By reducing the torque from the secondelectrical machine 16, the fifth coupling element 93 may be brought to asubstantially zero torque state in relation to the countershaft 18. Whena substantially zero torque state has arisen, the fifth coupling element93 is disengaged, so that the fifth cogwheel 92 of the fifth gear pair21 is disconnected from the countershaft 18.

Subsequently, with the help of the second electrical machine 16, therotational speed of the countershaft 18 is synchronized with therotational speed of the third cogwheel 76, following which the thirdcoupling element 88 is controlled in such a way that it connects thethird cogwheel 76 with the countershaft 18. When this connection hasbeen completed, the propulsion torque may be shared between thecombustion engine 4, the first electrical machine 14 and the secondelectrical machine 16. Finally, the second planetary wheel carrier 51 isrotational speed synchronized with the second sun wheel 32, followingwhich the second coupling device 58 connects the second planetary wheelcarrier 51 and the second sun wheel 32 with each other.

The second main shaft 36 now rotates, operated by the output shaft 97 ofthe combustion engine 4, and the second main shaft 36 operates thesecond pinion gear 68. Since the second cogwheel 70 is in engagementwith the second pinion gear 68 and is connected with the countershaft 18via the second coupling element 86, the second cogwheel 70 will operatethe countershaft 18, which in turn operates the third cogwheel 76 on thecountershaft 18. The third cogwheel 76 in turn operates the first mainshaft 34 via the third pinion gear 74, and the output shaft 20 of thegearbox 2 is thus operated via the coupling mechanism 96, which connectsthe first main shaft 34 and the output shaft 20 of the gearbox 2. Thevehicle 1 is now driven in a fifth gear.

In order to shift from a fifth to a sixth gear, the locking between thesecond sun wheel 32 and the second planetary wheel carrier 51 mustcease, which is achieved by way of controlling the first and/or thesecond electrical machine 14, 16 in such a way that torque balanceprevails in the second planetary gear 12, following which the secondcoupling device 58 is controlled in such a way that it disconnects thesecond sun wheel 32 and the second planetary wheel carrier 51 from eachother. A sixth gear is subsequently connected, by way of the controldevice 48 controlling the first and/or the second electrical machine 14,16 in such a way that a synchronous rotational speed arises between thefirst planetary wheel carrier 50 and the first sun wheel 26, to achievea locking between the first planetary wheel carrier 50 and the first sunwheel 26. This is achieved by way of controlling the first couplingdevice 56 in such a way that the first planetary wheel carrier 50 andthe first sun wheel 26 are mechanically connected with each other. Bysynchronizing the control of the combustion engine 2, and the second andfirst electrical machine 14 and 16, respectively, a soft anddisruption-free transition from a fifth to a sixth gear may be carriedout.

The first main shaft 34 now rotates operated by the output shaft 97 ofthe combustion engine 4, whereat the first main shaft 34 operates theoutput shaft 20 of the gearbox 2 via the coupling mechanism 96, whichconnects the first main shaft 34 and the output shaft 20 of the gearbox2. The vehicle 1 is now driven in a sixth gear.

In order to shift from a sixth to a seventh gear, the third cogwheel 76on the countershaft 18 must first be disconnected from the countershaft18 with the third coupling element 88, so that the third cogwheel 76 mayrotate freely in relation to the countershaft 18. Subsequently, thecountershaft 18 is connected with the first cogwheel 64 on thecountershaft 18 via the first coupling element 84. When the countershaft18 and the first cogwheel 64 on the countershaft 18 have a synchronousrotational speed, the first coupling element 84 is controlled in such away that the first cogwheel 64 and the countershaft 18 are connected.

In order to complete the shift from a sixth gear to a seventh gear, thelocking between the first sun wheel 26 and the first planetary wheelcarrier 50 must cease, which is achieved by way of the first and/or thesecond electrical machine 14, 16 being controlled in such a way thattorque balance prevails in the first planetary gear 10, following whichthe first coupling device 56 is controlled in such a way that itdisconnects the first sun wheel 26 and the first planetary wheel carrier50 from each other. Subsequently, the combustion engine 4 is controlledin such a way that a synchronous rotational speed arises between thesecond sun wheel 32 and the second planetary wheel carrier 51, so thatthe second coupling device 58 may be engaged in order thus to connectthe second sun wheel 32 with the second planetary wheel carrier 51, viathe coupling sleeve 57. By synchronizing the control of the combustionengine 2 and the second and first electrical machine 14 and 16,respectively, a soft and disruption-free transition from a sixth to aseventh gear may be carried out.

The second main shaft 36 now rotates with the same rotational speed asthe output shaft 97 of the combustion engine 4, and the second mainshaft 36 operates the second pinion gear 68. Since the second cogwheel70 is in engagement with the second pinion gear 68 and is connected withthe countershaft 18, the second cogwheel 70 will operate thecountershaft 18, which in turn operates the fifth cogwheel 64 on thecountershaft 18. The first cogwheel 64 in turn operates the first mainshaft 34 via the first pinion gear 62, and the output shaft 20 of thegearbox 2 is thus operated via the coupling mechanism 96, which connectsthe first main shaft 34 and the output shaft 20 of the gearbox 2. Thevehicle 1 is now driven in a seventh gear.

According to the embodiment above, the gearbox 2 comprises pinion gears62, 68, 74, 80 and cogwheels 64, 70, 76, 82 arranged on the main shafts34, 36 and the countershaft 18, respectively, to transfer rotationalspeed and torque. However, it is possible to use another type oftransmission, such as chain and belt drives, to transfer rotationalspeed and torque in the gearbox 2.

The transmission device 19 has four gear pairs 60, 66, 72, 78 accordingto the example embodiment. However, the transmission device 19 maycomprise any number of gear pairs.

It is also possible to carry out two-step shifts starting from the firstgear, and further to the third gear. From the third gear a shift is thencarried out to the fourth gear, and further to the fifth gear. Finally,it is possible to carry out a two-step shift from the fifth to theseventh gear. Below is a description of a shift from the first to theseventh gear, comprising a two-step shift from the first to the thirdgear, and a two-step shift from the fifth to the seventh gear. Such ashifting process need not be carried out in a sequence, but it ispossible to shift from, for example, the fifth to the seventh gearduring operation, independently of the gear steps that have beencompleted previously. It is also possible to carry out two-step shiftsin the form of down-shifts from the seventh gear to the fifth gear, andfrom the third gear to the first gear.

To begin with, the first gear is engaged by way of engaging gears in thegearbox 2, corresponding to the at least one gear pair G1, 60, 72, whichis connected with the first planetary gear 10, and the gear pair G2, 66,78, which connected with the second planetary gear 12 and the outputshaft 20.

With the second coupling device 58, the second sun wheel 32, arranged inthe second planetary gear 12, and the second planetary wheel carrier 51are connected with each other. At least one gear pair G3, 21, which isconnected with the countershaft 18 and the output shaft 20, is connectedto the countershaft 18 via the fifth coupling element 93, in order totransfer torque to the output shaft 20. The vehicle 1 is now driven withthe first gear engaged.

In order to carry out a two-step shift to the third gear, the firstelectrical machine 14 is activated in such a way that the firstelectrical machine 14 generates a propulsion torque on the output shaft20 via the at least one gear pair G1, 60, 72, which is connected withthe first planetary gear 10 and the output shaft 20, and via the atleast one gear pair G3, 21, which is connected with the countershaft 18and the output shaft 20.

Subsequently, the at least one gear pair G2, 66, 78, which is connectedwith the second planetary gear 12 and the output shaft 20, isdisconnected from the countershaft 18 which gear pair was previouslyconnected, by controlling the second electrical machine 16 and thecombustion engine 4, connected with the first planetary gear 10, in sucha way that a substantially zero torque state is achieved between the atleast one gear pair G2, 66, 78, which is connected on the countershaft18 and which is connected with the second planetary gear 12 and theoutput shaft 20, and the countershaft 18;

In the next step, the at least one gear pair G2, 66, 78, which isconnected with the second planetary gear 12 and the output shaft 20which gear pair was not previously connected to the countershaft 18, isconnected by controlling the combustion engine 4 in such a way that asynchronous rotational speed is achieved between the at least one gearpair G2, 66, 78, which is connected with the second planetary gear 12and the output shaft 20 which gear pair was not previously connected,and the countershaft 18.

Finally, the combustion engine 4 and/or the second electrical machine 16is activated, so that the combustion engine 4 and/or the secondelectrical machine 16 generates a propulsion torque on the output shaft20, via the at least one gear pair G2, 66, 78, which is connected withthe second planetary gear 12 and the output shaft 20, and which is nowconnected to the countershaft (18). The vehicle 1 is now driven with thethird gear engaged.

A two-step shift in a sequence from the third gear to the fifth gear isnot feasible, and instead a shift is carried out from the third gear tothe fourth gear, which is described above, and subsequently a shift fromthe fourth to the fifth gear is carried out, which is also describedabove.

In order to carry out a two-step shift from the fifth gear to theseventh gear, gears in the gearbox corresponding to the at least onegear pair G1, 60, 72, which is connected with the first planetary gear10, and the at least one gear pair G2, 66, 78, which is connected withthe second planetary gear 12 and the output shaft 20 are engaged in thegearbox 2. The coupling mechanism 96, which is arranged between thefirst planetary gear 10 and the output shaft 20, has been connected, bycontrolling the combustion engine 4, in such a way that a synchronousrotational speed has been achieved between the first planetary gear 10and the output shaft 20.

Subsequently, the first electrical machine 14 is activated, so that thefirst electrical machine 14 generates a propulsion torque on the outputshaft 20 via the coupling mechanism 96, following which the at least onegear pair G2, 66, 78, which is connected with the second planetary gear12 and the output shaft 20, is disconnected from the countershaft 18, byway of the second electrical machine 16 and the combustion engine 4,connected with the first planetary gear 10, being controlled in such away that a substantially zero torque state is achieved between the atleast one gear pair G2, 66, 78, which is connected on the countershaft18 and which is connected with the second planetary gear 12 and theoutput shaft 20, and the countershaft 18. Thereafter, at least the onegear pair G2, 66, 78, which is connected to the second planetary gear 12and the output shaft 20 which gear pair previously had not beenconnected when then fifth gear was engaged, is connected to thecountershaft 18, by means of controlling the combustion engine 4 in sucha way that a synchronous rotational speed is achieved between at leastone gear pair G2, 66, 78, which is connected to the second planetarygear 12 and the output shaft 20, and the countershaft 18. Finally, thesecond electrical machine 16 and the combustion engine 4, connected withthe first planetary gear 10, are controlled to generate a propulsiontorque on the output shaft 20. The vehicle 1 is now driven with theseventh gear engaged.

It is also possible to carry out two-step shifts in the form ofdown-shifts from the seventh gear to the fifth gear, and from the thirdgear to the first gear. This is carried out in a similar manner as anup-shift, but with a corresponding sequence with reversed gear pairs.

FIG. 4 shows a flow chart, relating to a method to control a hybridpowertrain 3, in order to achieve shifting of gears without torqueinterruption, comprising a combustion engine 4; a gearbox 2 with aninput shaft 8 and an output shaft 20, which combustion engine isconnected to the input shaft 8; a first planetary gear 10, which isconnected to the input shaft 8; a second planetary gear 12, which isconnected to the first planetary gear 10; a first electrical machine 14,which is connected to the first planetary gear 10; a second electricalmachine 16, which is connected to the second planetary gear 12; at leastone gear pair G1, 60, 72, connected with the first planetary gear 10 andthe output shaft 20; and at least one gear pair G2, 66, 78, connectedwith the second planetary gear 12 and the output shaft 20 , which gearpairs G1, 60, 72; G2, 66, 78 are connected to the output shaft 20 via acountershaft 18.

The method according to the invention comprises the steps:

-   -   a) engaging gears in the gearbox 2, corresponding to the at        least one gear pair G1, 60, 72, which is connected with the        first planetary gear 10, and the at least one gear pair G2, 66,        78, which is connected with the second planetary gear 12 and the        output shaft 20;    -   b) connecting two rotatable components 28, 32, 51 in the second        planetary gear 12 with a second coupling device 58;    -   f) locking a coupling mechanism 96, which is arranged between        the first planetary gear 10 and the output shaft 20, by        controlling the combustion engine 4, in such a way that a        synchronous rotational speed is achieved between the first        planetary gear 10 and the output shaft 20;    -   g) activating the first electrical machine 14, so that the first        electrical machine 14 generates a propulsion torque on the        output shaft 20 via the coupling mechanism 96;    -   h) disconnecting the at least one gear pair G2, 66, 78, which is        connected with the second planetary gear 12 and the output shaft        20, from the countershaft 18 which gear pair was connected in        step e), by controlling the second electrical machine 16 and the        combustion engine 4, connected with the first planetary gear 10,        in such a way that a substantially zero torque state is achieved        between the at least one gear pair G2, 66, 78, which is        connected on the countershaft 18 and which is connected with the        second planetary gear 12 and the output shaft 20, and the        countershaft 18;    -   i) connecting the at least one gear pair G2, 66, 78, which is        connected with the second planetary gear 12 and the output shaft        20 which gear pair was not connected in step e), to the        countershaft 18, by controlling the combustion engine 4, in such        a way that a synchronous rotational speed is achieved between        the at least one gear pair G2, 66, 78, which is connected with        the second planetary gear 12 and the output shaft 20, and which        gear pair was not connected in step e), and the countershaft 18;        and    -   j) controlling the second electrical machine 16 and the        combustion engine 4, connected with the first planetary gear 10,        in order to generate a propulsion torque on the output shaft 20.

Preferably, step b) comprises control of the combustion engine 4, insuch a way that a synchronous rotational speed is achieved between thetwo rotatable components 28, 32, 51 in the second planetary gear 12,following which the first coupling device 58 is shifted, and locks thetwo rotatable components 28, 32, 51 of the second planetary gear 12 witheach other.

Preferably, the at least one gear pair G1, 60, 72, which is connectedwith the first planetary gear 10 and the output shaft 20, comprises afirst pinion gear 62 and a first cogwheel 64 in engagement with eachother, which first pinion gear 62 is fixedly arranged with the firstplanetary gear 10, and which first cogwheel 64 is arranged so that itmay be connected with and disconnected from the countershaft 18;

a third pinion gear 74 and a third cogwheel 76 engaged with each other,which third pinion gear 74 is fixedly arranged with the first planetarygear 10, and which third cogwheel 76 is arranged so that it may beconnected with or disconnected from the countershaft 18, wherein in stepa) the first or the third cogwheel 64, 76 is connected to thecountershaft 18.

Preferably, the at least one gear pair G2, 66, 78, which is connectedwith the second planetary gear 12 and the output shaft 20, comprises asecond pinion gear 68 and a second cogwheel 70 in engagement with eachother, which second pinion gear 68 is fixedly arranged with the secondplanetary gear 12, and which second cogwheel 70 is arranged so that itmay be connected with and disconnected from the countershaft 18; andalso comprises a fourth pinion gear 80 and a fourth cogwheel 82 engagedwith each other, which fourth pinion gear 80 is fixedly arranged withthe second planetary gear 12, and which fourth cogwheel 82 is arrangedso that it may be connected with or disconnected from the countershaft18, wherein after step a), in step d) the second or the fourth cogwheel70, 82 is connected to the countershaft 18.

Preferably the combustion engine 4 is connected with a first planetarywheel carrier 50, which is connected with a second sun wheel 32 arrangedin the second planetary gear 12.

Preferably, the combustion engine 4 is connected with a first planetarywheel carrier 50 in the first planetary gear 10, which is connected witha second sun wheel 32, arranged in the second planetary gear 12.

Preferably, the two rotatable components 28, 32, 51 of the secondplanetary gear 12 comprise a second sun wheel 32 and a second planetarywheel carrier 51.

According to the invention, a computer program P is provided, stored inthe control device 48 and/or the computer 53, which may compriseprocedures to control the hybrid powertrain 3 according to the presentinvention.

The program P may be stored in an executable manner, or in a compressedmanner, in a memory M and/or a read/write memory R.

The invention also relates to a computer program product, comprisingprogram code stored in a medium readable by a computer, in order toperform the method steps specified above, when said program code isexecuted in the control device 48, or in another computer 53 connectedto the control device 48. Said program code may be stored in anon-volatile manner on said medium readable by a computer 53.

The components and features specified above may, within the framework ofthe invention, be combined between different embodiments specified.

1. A method to control a hybrid powertrain, comprising a combustionengine; a gearbox with an input shaft and an output shaft, whichcombustion engine is connected to the input shaft; a first planetarygear, which is connected to the input shaft; a second planetary gear,connected to the first planetary gear; a first electrical machine,connected to the first planetary gear; a second electrical machine,connected to the second planetary gear; at least one gear pair connectedwith the first planetary gear and the output shaft; and at least onegear pair connected with the second planetary gear and the output shaft,which gear pairs are connected to the output shaft via a countershaft,said method comprising the steps: a) engaging gears in the gearbox,corresponding to the at least one gear pair, which is connected with thefirst planetary gear, and the at least one gear pair, which is connectedwith the second planetary gear and the output shaft b) connecting tworotatable components in the second planetary gear with a couplingdevice; , f) locking a coupling mechanism, which is arranged between thefirst planetary gear and the output shaft, by controlling the combustionengine, in such a way that a synchronous rotational speed is achievedbetween the first planetary gear and the output shaft; g) activating thefirst electrical machine, so that the first electrical machine generatesa propulsion torque on the output shaft via the coupling mechanism; h)disconnecting the at least one gear pair, which is connected with thesecond planetary gear and the output shaft, from the countershaft whichgear pair was connected in step a), by controlling the second electricalmachine and the combustion engine, connected with the first planetarygear, in such a way that a zero torque state is achieved between the atleast one gear pair, which is connected on the countershaft and which isconnected with the second planetary gear and the output shaft, and thecountershaft; i) connecting the at least one gear pair, which isconnected with the second planetary gear and the output shaft which gearpair was not connected in step a), to the countershaft, by controllingthe combustion engine in such a way that a synchronous rotation speed isachieved between the at least one gear pair, which is connected with thesecond planetary gear and the output shaft and which gear pair was notconnected in step a), and the countershaft; and j) controlling thesecond electrical machine and the combustion engine, connected with thefirst planetary gear, in order to generate a propulsion torque on theoutput shaft.
 2. A method according to claim 1, wherein step b)comprises control of the combustion engine, in such a way that that asynchronous rotation speed is achieved between the two rotatablecomponents of the second planetary gear, following which the couplingdevice is shifted, and locks the two rotatable components in the secondplanetary gear with each other.
 3. A method according to claim 1,wherein the at least one gear pair, which is connected with the firstplanetary gear and the output shaft, comprises a first pinion gear and afirst cogwheel in engagement with each other, which first pinion gear isfixedly arranged with the first planetary gear, and which first cogwheelis arranged so that it may be connected with and disconnected from thecountershaft; on the other hand comprises a third pinion gear and athird cogwheel engaged with each other, which third pinion gear isfixedly arranged with the first planetary gear and which third cogwheelis arranged so that it may be connected with or disconnected from thecountershaft, wherein in step a) the first or the third cogwheel isconnected to the countershaft
 4. A method according to claim 1, whereinany of tho the at least one gear pair, connected with the secondplanetary gear and the output shaft, in the one hand comprises a secondpinion gear and a second cogwheel in engagement with each other, whichsecond pinion gear is fixedly arranged with the second planetary gearand which second cogwheel is arranged on a countershaft, so that it maybe connected and disconnected; comprises a fourth pinion gear and afourth cogwheel engaged with each other, which fourth pinion gear isfixedly arranged with the second planetary gear and which fourthcogwheel is arranged so that it may be connected with or disconnectedfrom the countershaft, wherein in step a) and before step b, in step d)the second or the fourth cogwheel is connected to the countershaft.
 5. Amethod according claim 1, wherein the combustion engine is connectedwith the first planetary wheel carrier in the first planetary gear,which is connected with a second sun wheel, arranged in the secondplanetary gear.
 6. A method according to claim 1, wherein in that instep b) the two rotatable components in the second planetary gearcomprise a second sun wheel and a second planetary wheel carrier.
 7. Avehicle with a hybrid powertrain, said hybrid powertrain comprising: acombustion engine; a gearbox with an input shaft and an output shaft,which combustion engine is connected to the input shaft; a firstplanetary gear, which is connected to the input shaft; a secondplanetary gear, connected to the first planetary gear; a firstelectrical machine, connected to the first planetary gear; a secondelectrical machine, connected to the second planetary gear; at least onegear pair, connected with the first planetary gear and the output shaft;at least one gear pair, connected with the second planetary gear and theoutput shaft, which gear pairs are connected to the output shaft via acountershaft; and an electronic control device configured for: a)engaging gears in the gearbox, corresponding to the at least one gearpair, which is connected with the first planetary gear, and the at leastone gear pair, which is connected with the second planetary gear and theoutput shaft; b) connecting two rotatable components in the secondplanetary gear with a coupling device; f) locking a coupling mechanism,which is arranged between the first planetary gear and the output shaft,by controlling the combustion engine, in such a way that a synchronousrotational speed is achieved between the first planetary gear and theoutput shaft: g) activating the first electrical machine, so that thefirst electrical machine generates a propulsion torque on the outputshaft via the coupling mechanism; h) disconnecting the at least one gearpair, which is connected with the second planetary gear and the outputshaft, from the countershaft which gear pair was connected in step a),by controlling the second electrical machine and the combustion engine,connected with the first planetary gear, in such a way that a zerotorque state is achieved between the at least one gear pair, which isconnected on the countershaft and which is connected with the secondplanetary gear and the output shaft, and the countershaft; i) connectingthe at least one gear pair, which is connected with the second planetarygear and the output shaft which gear pair was not connected in step a),to the countershaft, by controlling the combustion engine in such a waythat a synchronous rotation speed is achieved between the at least onegear pair, which is connected with the second planetary gear and theoutput shaft, and which gear pair was not connected in step a), and thecountershaft; and j) controlling the second electrical machine and thecombustion engine, connected with the first planetary gear, in order togenerate a propulsion torque on the output shaft.
 8. (canceled)
 9. Acomputer program product comprising computer program code stored on anon-transitory computer readable medium readable by a computer, saidcomputer program product used to control a hybrid powertrain, comprisinga combustion engine; a gearbox with an input shaft and an output shaft,which combustion engine is connected to the input shaft; a firstplanetary gear, which is connected to the input shaft; a secondplanetary gear, connected to the first planetary gear; a firstelectrical machine, connected to the first planetary gear; a secondelectrical machine, connected to the second planetary gear; at least onegear pair connected with the first planetary gear and the output shaft;and at least one gear pair connected with the second planetary gear andthe output shaft, which gear pairs are connected to the output shaft viaa countershaft, said computer program code comprising computerinstructions to cause one or more computer processors to perform theoperations of: a) engaging gears in the gearbox, corresponding to the atleast one gear pair, which is connected with the first planetary gear,and the at least one gear pair, which is connected with the secondplanetary gear and the output shaft; b) connecting two rotatablecomponents in the second planetary gear with a coupling device; f)locking a coupling mechanism which is arranged between the firstplanetary gear and the output shaft, by controlling the combustionengine, in such a way that a synchronous rotational speed is achievedbetween the first planetary gear and the output shaft; g) activating thefirst electrical machine, so that the first electrical machine generatesa propulsion torque on the output shaft via the coupling mechanism; h)disconnecting the at least one gear pair, which is connected with thesecond planetary gear and the output shaft, from the countershaft whichgear pair was connected in step a), by controlling the second electricalmachine and the combustion engine, connected with the first planetarygear, in such a way that a zero torque state is achieved between the atleast one gear pair, which is connected on the countershaft and which isconnected with the second planetary gear and the output shaft, and thecountershaft; i) connecting the at least one gear pair, which isconnected with the second planetary gear and the output shaft which gearpair was not connected in step a), to the countershaft, by controllingthe combustion engine in such a way that a synchronous rotation speed isachieved between the at least one gear pair, which is connected with thesecond planetary gear and the output shaft, and which gear pair was notconnected in step a), and the countershaft; and j) controlling thesecond electrical machine and the combustion engine, connected with thefirst planetary gear, in order to generate a propulsion torque on theoutput shaft.